
/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 *版权所有2002-2017原作者。
 *
 *根据Apache许可证2.0版（“许可证”）获得许可；
 *除非符合许可证，否则不得使用此文件。
 *您可以在以下地址获取许可证副本：
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *除非适用法律要求或书面同意，软件
 *根据许可证分发的内容是按“原样”分发的，
 *无任何明示或暗示的保证或条件。
 *有关管理权限和
 *许可证下的限制。
 */

package org.springframework.beans.factory.config;

import java.io.IOException;
import java.util.Properties;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.io.support.PropertiesLoaderSupport;
import org.springframework.lang.Nullable;

/**
 * Allows for making a properties file from a classpath location available
 * as Properties instance in a bean factory. Can be used to populate
 * any bean property of type Properties via a bean reference.
 *
 * <p>Supports loading from a properties file and/or setting local properties
 * on this FactoryBean. The created Properties instance will be merged from
 * loaded and local values. If neither a location nor local properties are set,
 * an exception will be thrown on initialization.
 *
 * <p>Can create a singleton or a new object on each request.
 * Default is a singleton.
 *
 * @author Juergen Hoeller
 * @see #setLocation
 * @see #setProperties
 * @see #setLocalOverride
 * @see java.util.Properties
 */
/**
 *允许从类路径位置创建可用的财产文件
 *作为bean工厂中的财产实例。可用于填充
 *通过bean引用的任何类型为财产的bean属性。
 *
 *<p>支持从财产文件加载和/或设置本地财产
 *在这个FactoryBean上。创建的财产实例将从
 *加载值和本地值。如果既没有设置位置也没有设置本地财产，
 *初始化时将引发异常。
 *
 *＜p＞可以在每个请求上创建一个单例或一个新对象。
 *默认为单例。
 *
 *@作者Juergen Hoeller
 *@参见#setLocation
 *@参见#setProperties
 *@参见#setLocalOverride
 *@参见java.util.Properties
 */
public class PropertiesFactoryBean extends PropertiesLoaderSupport
		implements FactoryBean<Properties>, InitializingBean {

	private boolean singleton = true;

	@Nullable
	private Properties singletonInstance;


	/**
	 * Set whether a shared 'singleton' Properties instance should be
	 * created, or rather a new Properties instance on each request.
	 * <p>Default is "true" (a shared singleton).
	 */
	/**
	 *设置共享的“singleton”财产实例是否应
	 *创建，或者在每个请求上创建一个新的财产实例。
	 *＜p＞默认值为“true”（共享单例）。
	 */
	public final void setSingleton(boolean singleton) {
		this.singleton = singleton;
	}

	@Override
	public final boolean isSingleton() {
		return this.singleton;
	}


	@Override
	public final void afterPropertiesSet() throws IOException {
		if (this.singleton) {
			this.singletonInstance = createProperties();
		}
	}

	@Override
	@Nullable
	public final Properties getObject() throws IOException {
		if (this.singleton) {
			return this.singletonInstance;
		}
		else {
			return createProperties();
		}
	}

	@Override
	public Class<Properties> getObjectType() {
		return Properties.class;
	}


	/**
	 * Template method that subclasses may override to construct the object
	 * returned by this factory. The default implementation returns the
	 * plain merged Properties instance.
	 * <p>Invoked on initialization of this FactoryBean in case of a
	 * shared singleton; else, on each {@link #getObject()} call.
	 * @return the object returned by this factory
	 * @throws IOException if an exception occurred during properties loading
	 * @see #mergeProperties()
	 */
	/**
	 *子类可以重写以构造对象的模板方法
	 *这家工厂退回的。默认实现返回
	 *普通合并的财产实例。
	 *＜p＞在初始化此FactoryBean时调用
	 *共享单例；否则，在每个｛@link#getObject（）｝调用上执行。
	 *@return此工厂返回的对象
	 *如果在加载财产期间发生异常，则@throws IOException
	 *@参见#mergeProperties（）
	 */
	protected Properties createProperties() throws IOException {
		return mergeProperties();
	}

}
